mllo g



Patented Oct. 26, 1897.

(No Model.)

M. G. KELLOGG. MULTIPLE SWITOHBOARD.

UNITED STATES PATENT OFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO TIIE KELLOGG SIVITCHBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent N0. 592,397, dated October 26, 1897.

Applicatioufiled May 16, 1891. Serial No. 392,966. (No model.)

To all whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates especially to a telephone-exchange system in which the lines are metallic-circuit lines and in which the necessary switching between the lines is accomplished by means of pairs of double or loop plugs connected together by double flexible cord conductors.

It consists, first, of a system of testing the lines at any board to determine whether or not they are in use; secondly, of an organization of loop-switches and connections for said cords by which the movements required of the operator in making the necessary connections and disconnections are few and convenient to make, and, thirdly, of an arrangement of the annunciatorsand switches of the difierent lines by which the clearing-out annunciators are included in a bridge-circuit with their respective pairs of cords.

In the accompanying drawings, illustrating my invention, Figure 1 represents sectional views of sections of two multiple switchboards and the main-line central-ofiice connections and apparatus of the two lines connected to the two switchboards. Fig. 2 represents a diagram of an operators cord system and apparatus necessary to illustrate my invention. Fig. 3 represents an operators test system.

I place as many switchboards in the central office as are found necessary or desirable in order to properly operate the exchange. In each board is a spring-jack switch for each line. Each switch has a contact-spring which normally connects with a contactpoint and is separated from the point while a plug is inserted into the switch and has a contact-piece insulated from the rest, except by the circuit connections. To the contact-point is attached an extension piece or connection along the surface of the switch-hole, by means of which one of the contact-pieces of the loop test-plug,

hereinafter described, forms connection with the contact-point when the plug is. inserted, as hereinafter described. The insulated contact-piece mentioned above is also placed along the surface of the switch-hole and preferably in front of said extension-piece to the contact-point, and is so placed that one of the contact-pieces of the loop-switch plugs, hereinafter described, forms connection with said contact -piece when the plug is inserted. Said plugs are constructed and said contactpieces and extension-pieces of the switches are so placed that when the test-plug is inserted into a switch the contact-piece of the plug does not come into contact with said contact-piece and when a switch-plug is inserted into a switch the contact-piece of the plug does not come into contact with the extension piece or point of the switch.

In Fig. 1, A A are sectional views of sections of the two switchboards shown. g g rep resent the springs of the difierent switches, h h the contact-points of the switches on which the springs normally rest, and h h the extension-pieces of the points placed along the surface of the holes of the switches in front of the points. j j are the insulated contact-pieces of the switches, also placed along the holes of their respective switches and preferably in front of the extension-pieces. a b are the rubber strips on which the metal parts of the switches are mounted and through the fronts of which are the switchholesl Z.- These holes are rectilinear holes and are adapted to receive the loop-plusg mentioned above and to cause them to operate the switches, as described. W and X are calling-annunciators, one for each line shown and each connected into the circuit of its line, as will hereinafter be described.

Each annunciator has a pair of contactpoints normally (or when the annunciator does not indicate a call) in contact with each other, but which are separated by the annunciator while it indicates a call. The two contact-points of a pair are marked 1) and q, respectively. One of them, q, is a spring-contact which is pressed by the annunciator-drop, when the drop falls, away from its corresponding contact-point p. 'lhc'contact-point p is represented as an angle-piece which passes generator is, of course, in the metallic circuit v 2,'D D area pair of loop-switch plugs adapted marked m, n, and 19, respectively.

spective boards as follows and as shown::

One side or branch of the line is connected to the contact-pieces jj of its switches on the several boards. The other side or; branch of the line passes successively through the pairs of contacts 9 h of its switches on the several boards, passing in each case to the spring first. ciator and the pair of contact-points p q of the annunciator, and is thence connected to the other side or branch of the line to which the contact-pieces j j are connected.

It then passes through its line-annun i The two branches of the line are normally on closed circuit at the subscribers station and maybe provided with any usual and appropriate subscribei"s-statio11 apparatus. The subscribers calling and clearing-out of the line when operated to send either calling or clearing-out signals.

In the operators cord system shown in Fig.

for-use with the switches shown in Fig. 1. r r are the rubber insulations of the plugs. S S are the two contact-pieces of .the plug. The plugs are constructed and the contactpieces are arranged so that when a plug is inserted into a switch the spring is pressed away from its contact-point.

The contacta piece S forms connection with the spring 9, the contact-piece S" forms connection with 5 the contact-piece j of the switch, and the 3 contact-point h is insulated from the con-i tact-pieces of the plug. inserted into the switches in such a direction that they form the connections as above described.

cordssh'own. if is the operators telephone. is her calling-generator. annunci-ator, and R is a resistance-coil.

at the will of the operator. a

V One contact-piece of one plug of the pair of plugs isconnected by a flexible conductor to one contact-piece of the other plug.

The plugs should he two other contact-pieces of the plugs are also connected together by a flexible conductor. One of said flexible conducting-circuits,which connects two of the contact-pieces of the pair of plugs, is connected to the lever of the switch. The other flexible conductin'g-circuit described above is connected to one side of the resistance-coil.

The other side of the i The three contact-points of the switch are They are placed adjoining each other in the order in which they are mentioned above and so that the lever alternately rests on each point as it is moved by the operator. The other side of the operators telephone isconnected to the contact-point m and the other side of the clearing-out annunciator is connected to the contact-point 19. One side of the operators calling-generator is connected to the last mentioned flexible conducting-circuit(that to which the resistance-coil is connected) and the other side is connected to the contactpoint it of the switch.

The lever of the switch Y normally rests on the contact-point 1%.

Only one pair of switch-plugs, with their cords, clearing-out annunciator, and switch, is shown. Other pairs, as are found desirable,

may be added to the operators systemin a way which will be apparent to those skilled in the art. She needs but one telephone, calling-generator, and resistance-coil.

In the operators test system shown in Fig. 3, T is the loop test-plug, t is the test receiving instrument, and B is a test-battery. u is the rubber insulation of the plug, and c c are its contact-pieces. The pin g is constructed and the pieces are arranged so that when the plug is inserted into any switch the spring is pressed away from its contact-point, the contact-piece 1 forms connection with the spring g, the contact-piece 1: forms connection with the extension-piece h, and the contact-piece j of the switch is not in cont-act with the contact-pieces of the plug. The plugs should be inserted into the switches in such adirection that they form the connections as above described.

The two contact-pieces 'v o of the plug are system, and they are conveniently mounted Y is the operators switch for the pair of 1 B c is a clearing-out The i switch has a lever and three contact-points, i on which the lever may be alternately placed 1 f the annunc'iator of a line, she places one of i the plugs D of a pair of her plugs in the switch of the line. The

at her board for her work. The conductingcords of the plugs should be long enough so that she-can connect any plug with any switch at her board. I

The operation of the switch system is as follows: When an operator receives a callon By so doing she opens the closed circuit of the line and loops her telephone into the circuit. The closed'ciri cuit of the line is opened at the pair of con- %,tacts g hot the switch. The two cords of the iplug are connected to the two branches of the I'line by the connection of the two contactpieoes of the plug with the two contact-pieces g and j otthe switch, and the two-cords are bridged or connected by a bridge circuit which contains the operators telephone and the resistance-coil. lVhen the operator finds out byconversation what line is wanted, she tests the line wanted, as will be hereinafter described, and it she finds it is not busy she places the other plug of the pair in the switch of the line, opening the closed circuit of the line and connecting its two branches to the cord-circuits of the plug. She then moves the lever of the switch so that it rests on the point 11. When the lever is in this position, the circuit is bridged by the operators generator and a signal-current from the generator goes in split current to the two lines. She then moves the lever of the switch so that itrests on p and the lines are connected in metallic circuit for conversation with the clearing-out annunciator and resistance-coil in a circuit which bridges the metallic circuit. hen the operator receives the clearing-out signal, she will remove the plugs from the switches and move the lever of the switch so that it rests on the point m when they are ready to be used for another connection.

The test receiving instrument and battery should be so constructed and adjusted to each other and the circuits of the exchange that the instrument will sound or respond when it and the battery are looped into the normal closed circuit of any line of the exchange, but will not respond when they are in open circuit or the line in which the test is made is looped into circuit with any other line, and has, therefore, the resistance of both lines in its circuit. This construction and adjustment can be readily accomplished and may be facilitated, if desired, by the addition of artificial resistances, so as to equalize the resistance of the various lines of the exchange. This construction and adjustment depends on the fact that an electromagnet may be readily made so as to operate when a battery and a certain resistance are in circuit with it and not to operate when the resistance is considerably larger. This operation can be obtained in different ways, dependent on the style of the electromagnet, the number of convolutions of its coil, the size of the battery, and the adjustment of the retractile spring. These parts should be such that the electromagnet will be actuated when the test system is looped into the normal circuit of any line of the exchange, but will not be actuated when the circuit is open or the additional resistance of another line is introduced.

The test system is as follows: When an operator at any board tests any line, she places her test-plug in the switch of the line, and by so doing connects the two contact-pieces of the plug with the two contact-points g h of the switch. If the line is not switched and its annunciator does not indicate a call, the test receiving instrument and battery will be included in the closed metallic circuit of the line and the instrument will sound, indicating that the line is free to be connected to. If, however, when the test is made the line is switched at some board and the plug is in serted in the cutoff portion of the line, the circuit of the test receiving instrument is open at the contact-points g h of the switch used in switching and the instrument will not sound. If, again, when the line is switched the test-plug is inserted inthe portion of the circuit which is included with the other line, the instrument will not sound, because the resistance is that of two lines combined. If, again, when the test is made the line is not switched at any board, but its annunciator indicates a call, the circuit is open at the pair of contact-points of the annunciator and the instrument will not sound. When, therefore, the test is made and the instrument does not sound, the operator knows that either the line is switched at some board or its annunciator indicates a call and she will not connect to the line.

In this system when two subscribers are connected together in metallic circuit for conversation and either the operators telephone or the clearing-out annunciatoris connected to the circuit, it is through a circuit which bridges the metallic circuit and which contains the resistance-coil. The resistance of this bridge-circuit may, by means of the resistance-coil, be made such as not to very materially affect the talking-circuit of the two lines.

Of course instead of the resistance of such a character as not to materially affect the talking-circuit of the two lines the telephone and the annunciator themselves may each readily be made of such character as to ofier the required resistance to telephone-currents.

In multiple-switchboard systems an operator to whom certain lines are assigned to answer frequently receives several calls at practically the same moment, and it may re quire some time before she can switch to a certain line and answer its call. In systems in which the test depends only on whether the line has been switched at some board another operator may test the line before there has been time to answer the call and may switch the line with another line, to the annoyance and confusion of both subscriber and operator who receives the call. The latter will be especially disturbed, because, having re ceived the call, she will consider that the line is free and will connect her telephone to it Without making a test, and will then find it impossible to carry on conversation with the calling subscriber, or will intercept the conversation going on between the two lines. In my system the line tests busy as soon as the call is indicated and any operator who tests the line before its call is answered will become aware of the fact that it is engaged and will not connect to the line and thereby disturb the satisfactory operation of the exchange.

I claim as my invention-- ,1. In atelephone-exchange system, a metallic-circuit line normally on closed circuit and with an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call, in combination with a test receiving instrument and battery and switch apparatus by which the instrument and battery may be looped into the normal circuit of the line,'the instrument being so constructed and adjusted that it will sound or respond when thus looped and the circuit in which it is included is neither open nor contains the resistance of two telephone-lines, but not otherwise, substantially as set forth.

- 2. In a telephone-exchange system, multiple switchboards and a metallic-circuit line connected to each of the boards and normally on closed circuit with an annunciator in the circuit having contact-points by which the circuit is open while the annunciator indicates a call, in combination with test receiving instruments, one at each board and connected in a loop with a test-battery, and

switching apparatus by which each instrument with its battery may at its board be looped intothe normal circuit of the line, the instrument being so constructed and adjusted that it will sound or respond when thus looped and the circuit in which it is included is neither open nor contains the resistance of two telephone-lines, substantially as set forth.

3. In a telephone-exchange system, multi-.

ple switchboards, metallic-circuit lines, each line connected to each board and normally on Closed circuit with an annunciator in its circuit with contact-points by which the circuit is open while the annunciator indicates of the lines may be connected together in metallic circuit, in combination withtest receiving instruments and batteries, one of each at g each board, and switch apparatus" by which each instrument with its battery may be ins rument being so constructed and adjusted that it will sound or respond when thus looped and the circuit is neither open nor contains the, resistance of two lines, but not otherwise,

substantially as set forth.

4:. In a telephone-exchange system, multiple switchboards and a metallic-circuit line normally on closed circuit and passing successively through pairs of switch contact-Y points, one pair on each board, and having normally in its circuit an annunciator with a pair of contact-points by which the circuit is open when the annunciator indicates a call,

in combination with switch apparatus at each board by which the two sides or branches of the line may be connected with the two sides or branches of any of the other lines and when they are thus connected at a board, said pair of switch contact-points at the boardis open, and loop test-plugs, one at each board, the

two contact-pieces of which are connected to the two sides, respectively, of a loop which contains a. test receiving instrument and battery, each plug being adapted to beinser-ted into the line-switchat its board and when in serted todisconnect the pair of contact-points of theswitch and connect them with the two contact-pieces of the plug, respectively, the instrument bcing so constructed and adjusted that it will sound or respond when thus switched into circuit and the circuit in which it is included is neither open nor contains the resistance of two telephone-lines, but not otherwise, substantially as set forth.

5. In a telephone-exchange system,- a pair of loop-switch plugs the two contact-pieces of one of which are connected to the two contactpieces of the other, respectively, by two flexible cord conductors, in combination with an 'operators telephone, a clearing-out annunciator, a calling-generator, and a switch having a lever connected to one of the conductors and three contacts connected respectively through the telephone, the generator and annunciator with the other conductor, said lever being adapted to be brought at will in connection with either contact, whereby the operator may at will bridge or cross-connect the cord-circuits through either the telephone, or the generator or the annunciator, substantially as set forth.

'6. In a telephone-exchange system, a pair of loop-switch plugs the two contact-pieces of one of which are connected to the two contactpieces of the other, respectively, by two flexible cord conductors in combination with an operators telephone, a clearing-out annunciator, a resistance-coil and a switch having 1 a lever connected to one of the conductors and a call, and switch apparatusby which any two two contacts connected respectively through the telephone annunciator to the resistance coil and through it with the other conductor, said-lever being adapted to be brought at will in connection with either contact, whereby the operator may at will bridge or cross-conloopedinto the normal circuit of any line,theg 1 nect the two cord-circuits through either the telephone and resistance-coil or the annunciator and resistance-coil, substantially as set forth.

7. In a telephone-exchange system, a pair l of loop-switch plugs the two contact-pieces of one of which are connected to the two contactpieces of the other, respectively, by two flexible-cord circuits, in combination with a switch having a movable lever and three contactbolts on which the lever may alternately be i laced ano erators tele hone acallin enerator and a clearing-out annunciator said le- 1 ver being connected to one of said cord-circuits, one of said bolts being connected to the other cord-circuit through the telephone, an-

- other of said bolts being connected to said 1 other cord-circuit through the generator and the third bolt being connected to said other 1 cord-circuit through the annunciator, sub

stantially as set forth.

8. In a telephone-exchange system, a pair of loop-switch plugs the two contact-pieces of one of which are connected to the two contactpieces of the other, respectively, by two flexible-cord circuits, in combination with a switch having a movable lever and three contactbolts on which the lever may be alternately erator and a clearing-out annunciator, said lever being connected to one of said cord-circuits, the bolt on which the lever normally rests being connected to the other cord-circ uit through the telephone, the next adjoining bolt being connected to said other cord circuit through the generator and the last bolt being connected to said other cord-circuit through the annunciator, substantially as set forth.

9. In a telephone-exchange system, two metallic-circuit lines temporarily connected together into a metallic circuit for conversation in combination with an operators telephone, a calling-generator, a clearing-out annunciator and a switch having a lever and three contact-bolts on which the lever may alternately be placed, one side of said metallic circuit being connected to the lever, the other side being connected through the telephone to one of said bolts, through the generator to another of said bolts and the annunciator to the third of said bolts, substantially as set forth.

10. In a telephone-exchange system, two

scribed my name.

MILO G. KELLOGG. WVitnesses:

FRANK S. OBER, EDWARD G. DAVIDSON. 

